1. Field of the Invention
This invention for sensing the wind's direction and velocity by directly measuring changes in the static boundary layer pressures of surfaces affected by the relative wind--has numerous aerodynamic applications to the practical science of aircraft flight.
In addition to its anemometric functions, this principle of boundary layer pressure measurement provides the incomparably accurate and reliable means of instrumenting aircraft for precision flight control at low airspeed.
Among the instrumentation which derives from this boundary layer principle are these several measurements:
(a) Calibrated airspeed; PA1 (b) Change of induced angle of attack; PA1 (c) Calibrated potential of the force of wing lift (POWL) PA1 (d) Calibrated propeller thrust; PA1 (e) Calibrated engine power output; PA1 (f) The balance of aerodynamic forces at any point on the airframe surface.
This invention relates to a new instrument and method for the precision management of the potential of lift of an aircraft wing and particularly relates to a new instrument and method for coincidentally measuring changes in the velocity and angle of incidence of the impinging wind as the mathematical product of functions of these two variables and for transmitting this product in the energy form of differential pressure.
2. Prior Art
The history of heavier-than-air-flight spans three-quarters of a century and many sophisticated and useful instruments have been developed for the control of cruising and of higher speed flight. However, instruments for controlling flight in the low speed range regimes of becoming airborne, climbing, descending and landing have not been improved significantly from the earliest beginning. Control of transitional flight remains primitive and uncertain because both angle of attach and airspeed vary widely with changes in wing loading, center of gravity and flap deployment.
Usually, the private pilot depends solely upon the airspeed indicator and upon the physical senses and sensations. The pilot is said to fly "by the seat of the pants". Larger and more powerful aircraft often have the highly uncertain use of some form of angle-of-attack indication. The U.S. Navy's flight arm depends heavily upon angle of attack indication for the control of transitional flight.
Neither airspeed nor angle of attack indication reliably identifies the critical conditions of wing lift. Neither is useful in mathematically identifying the critical, incremental loss of dynamic lift which causes the differential onset of mushing sink. Neither can mathematically identify the maximum angle of climb, which is the "Vx" defined by the Federal Aviation Administration.
Today's accident statistics illuminate the need for flight instrumentation by which transitional flight can be controlled knowledgeably and intelligently: Of the four thousand non-scheduled, non-military aircraft accidents annually reported to the National Transportation Safety Board, relatively few occur which are unrelated to transitional flight and which do not involve uncontrolled collision with the ground (or water). Year after year, some four hundred General Aviation pilots and one hundred peacetime Naval aviators are killed in this same type of loss-of-control-at-low-altitude accident. Since the 1945 ending of World War II, more than ten thousand General Aviation pilots have died in the typical mush/stall/spin accident for want of specific transitional flight instrumentation.
Numerous "wind shear" disasters have been suffered by scheduled air carriers and by other aircraft in prematurely striking the ground on approach to landing and shortly after liftoff. Probably no such accident would occur that is attributable to wind shear if aircraft were adequately instrumented to sensitively display changes in the velocity and the direction of the relative wind. Unfortunately, in the known prior art, there is no instrument capable of detecting and warning of wind shear until too late for effective corrective action.